State is persistent ? about triotp

[linkdd]

Hello @jbjuin

Thanks for the feedback 😄

I think you're talking about the state of a gen_server. In that case, no the state is not restored (same for the real OTP).

The state of a gen_server is temporary and lives only in memory. It's very common to have a connection handle to a database as state for example. If a temporary network failure occurs, the gen_server will crash and be restarted by the parent supervisor, creating a new connection (successfully once the temporary network failure is resolved).

If you need persistance, the real OTP gives you:

• ETS (Erlang Term Storage), an in-memory key/value store that runs in its own process (or task)
• DETS (Distributed ETS), which is replicated/balanced over the cluster. We can't do that here, this library does not support clustering (yet???)
• Mnesia, which is based on DETS and allows on-disk persistance (if you know RabbitMQ, that's what they use to store the messages)

Yes, in the Erlang/Elixir world you don't need Redis 😉

TL;DR: If you need persistance over restarts, you should rely on an external service like Redis, Memcached, or a database, and hold the connection to this service in the gen_server's state